ok I didn't say clear

He didn't learn 微积分 yet, The first 微积分 class, teacher gave a 微积分 question, suppose nobody know how to resolve it. My son use what he learned in geometry in 6th grade to resolve that problem. one example about those two geometry books are very good. I don't know much about math and seems you know a lot. you must know how to use geometry principles to resolve 微积分 question.